Recently, a control device has been proposed that supplies/interrupts an electric current that flows through a wire connected between a battery and a load by turning on/off a switch that is provided at an intermediate position of the wire. The wire generates Joule heat when an electric current flows through the wire. Even when no over current flows through the wire, the Joule heat may possibly exceed the heat radiation amount of the wire. If the Joule heat exceeds the heat radiation amount of the wire, the temperature of the wire will increase in the course of time in which the electric current flows through the wire, and smoke will be generated when the temperature of the wire exceeds a predetermined temperature.
Conventional control devices for supplying/interrupting an electric current that flows through a wire encompass a control device (see Patent Document 1, for example) for calculating a temperature of a wire and interrupting an electric current flowing through the wire if the calculated temperature exceeds a predetermined temperature, in order to prevent smoke generation of the wire.
The control device disclosed in Patent Document 1 detects the electric current flowing through the wire in a predetermined first cycle, and calculates the temperature of the wire based on the detected current value. The control device disclosed in Patent Document 1 interrupts the electric current flowing through the wire if the calculated temperature of the wire exceeds a predetermined first temperature that is close to the smoke generation temperature. Accordingly, smoke generation of the wire is prevented.
Furthermore, if the calculated temperature of the wire is lower than a predetermined second temperature that is lower than the first temperature and is close to the ambient temperature of the wire, the control device disclosed in Patent Document 1 detects the electric current flowing through the wire in a predetermined second cycle that is longer than the first cycle, and calculates the temperature of the wire based on the detected current value. Accordingly, the control device disclosed in Patent Document 1 reduces the number of times of the calculation of the wire temperature if the temperature of the wire is lower than the second temperature, realizing low power consumption.